Update Sequelize from 5.13.1 to 5.15.1

Author: devmarantz

package.json

@@ -28,7 +28,7 @@
     "passport": "^0.4.0",
     "passport-jwt": "^4.0.0",
     "pg": "^7.12.1",
-    "sequelize": "^5.13.1",
+    "sequelize": "^5.15.1",
     "uuid": "^3.3.2",
     "validate.js": "^0.13.1"
   },